title: Soil warming alters microbial substrate use in alpine soils.
abstract: Will warming lead to an increased use of older soil organic carbon (SOC) by microbial communities, thereby inducing C losses from C-rich alpine soils? We studied soil microbial community composition, activity, and substrate use after 3 and 4 years of soil warming (+4 °C, 2007-2010) at the alpine treeline in Switzerland. The warming experiment was nested in a free air CO2 enrichment experiment using depleted (13)CO2 (δ(13)C = -30‰, 2001-2009). We traced this depleted (13)C label in phospholipid fatty acids (PLFA) of the organic layer (0-5 cm soil depth) and in C mineralized from root-free soils to distinguish substrate ages used by soil microorganisms: fixed before 2001 ('old'), from 2001 to 2009 ('new') or in 2010 ('recent'). Warming induced a sustained stimulation of soil respiration (+38%) without decline in mineralizable SOC. PLFA concentrations did not reveal changes in microbial community composition due to soil warming, but soil microbial metabolic activity was stimulated (+66%). Warming decreased the amount of new and recent C in the fungal biomarker 18:2ω6,9 and the amount of new C mineralized from root-free soils, implying a shift in microbial substrate use toward a greater use of old SOC. This shift in substrate use could indicate an imbalance between C inputs and outputs, which could eventually decrease SOC storage in this alpine ecosystem.
authors.affiliation: Paul Scherrer Institute (PSI), Laboratory of Atmospheric Chemistry, Villigen PSI, 5232, Switzerland.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Streit
authors.forename: Frank
authors.initials: F
authors.lastname: Hagedorn
authors.forename: David
authors.initials: D
authors.lastname: Hiltbrunner
authors.forename: Magdalena
authors.initials: M
authors.lastname: Portmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Saurer
authors.forename: Nina
authors.initials: N
authors.lastname: Buchmann
authors.forename: Birgit
authors.initials: B
authors.lastname: Wild
authors.forename: Andreas
authors.initials: A
authors.lastname: Richter
authors.forename: Sonja
authors.initials: S
authors.lastname: Wipf
authors.forename: Rolf T W
authors.initials: RT
authors.lastname: Siegwolf
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism; D017753:Ecosystem; D005227:Fatty Acids / Q000032:analysis; D028221:Larix; D059013:Microbial Consortia; D010743:Phospholipids / Q000032:analysis; D028223:Pinus; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013557:Switzerland; D013696:Temperature
chemical_list: D005227:Fatty Acids; D010743:Phospholipids; D012987:Soil; D002244:Carbon
keywords: Larix decidua; Pinus mugo; continuous 13C labeling; free air CO2 enrichment (FACE); fungi; gram negative bacteria; gram positive bacteria; phospholipid fatty acids (PLFA); soil warming